WHEN we speak in December, Glen Mazzara is the showrunner of cult hit The Walking Dead. Or, as he puts it to me, ''I would be the equivalent of the CEO of the show'', overseeing a team of about 150 people, steering the program creatively and financially, hiring and firing actors, crew, directors and producers, and liaising with the suits at AMC, the cable channel that pays for it all (and, incidentally, pays for Mad Men and Breaking Bad).

But a couple of weeks after we speak, Mazzara - who took over the show from Shawshank Redemption director Frank Darabont after season one - is gone, officially by mutual consent. ''Both parties acknowledge that there is a difference of opinion about where the show should go moving forward, and conclude that it is best to part ways,'' the AMC statement says.

''It's time to move on,'' says Mazzara, who declines my request for a follow-up interview, just as he has declined all other interview requests since the shock announcement a few days before Christmas.

For now, though, Mazzara is still with the show, having agreed to see season three through to its conclusion. You might say he has joined the ranks of the walking dead himself.

Whatever the details of the split, there is nothing in our chat to suggest Mazzara saw it coming. Talking about creative control, he says: ''For the most part I have final cut.'' If he and the network saw things differently, he felt he could argue his case and would be heard. ''AMC has been so supportive of the creative process.''

Mazzara is due in Australia in late February to share his understanding of the showrunner experience as part of a three-day television writing studio in Melbourne and Sydney. The Walking Dead is the third show he has run. ''The first two were not as successful,'' he says. ''I think you learn by doing. You go to war a few times to become a veteran.'' He offers a glimpse of what he will be talking about as he describes the process of creating a series.

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For six weeks, the writers - there are seven in all, including himself and Robert Kirkman, co-creator of the comic-book series on which the show is based - plot the story arc for the coming season. They then pitch it to the studio. Once they have approval, the scripts are doled out, and each writer gets about two weeks to write a draft. And then, he says, ''we'll rewrite the script many times''.

''I'm not a person who thinks the first draft is the best draft,'' he adds, saying ''it's a real challenge for the writers because there's a very high bar for the material and I'm never satisfied''.

Mazzara says he takes notes - suggestions or critiques - from actors, producers and studio executives, and these inform the rewrites. It is ''very conceivable I may do two dozen different drafts, all very different''.

When the script is ready, he has a three-hour meeting with the director. ''We call it the tone meeting - I go through the script scene by scene, line by line, and I tell the director everything I can about why this script is the way it is. This is what it means thematically, this is what we're hoping for, this is maybe a challenge in the scene. And then I turn it over to the director and the actors and I really don't have a lot of input while they're shooting; I move on to the next script.''

It's an exhaustive process but it has clearly paid dividends. The show has been a critical and ratings smash in the US, and has developed enough of a cult following in Australia that pay TV channel FX rushes it to air just hours after it screens in the US.

''The show is a success in every sense of the word,'' Mazzara says. ''Hopefully, we'll be around for a long time.'' (AMC has commissioned a fourth season, sans Mazzara.)

Why, I wonder, does he think the zombie genre resonates so much? After all, while The Walking Dead is rare in taking it to television, there has been an explosion of interest in the genre in other forms - graphic novel, film, computer game, flash-mob event - in the past decade. ''People really do believe that some sort of apocalypse is coming and people are going to have to bond together to survive, and the infrastructure of society and government will collapse,'' he says.

He adds that people buy into this survivalist vision because ''it's a very accessible fantasy … they imagine, 'What would my life be like if I had no food, no water and only a couple of guns and had to protect my family and my neighbours?' It's satisfying to people to be able to have a very simple hunter-gatherer existence. We're back in the food chain, there's a small tribe on the road trying to make it through the day.''

He and his team craft situations in which the characters have difficult decisions to make. ''In a sense, the audience plays along at home. They say, 'I would save that guy even if it means risking my neck,' or, 'No, I would shoot him so that I could get away,' and they scream at the TV. It feels like an immersive experience.''

It also caters, he admits, to a far baser instinct. ''You're shooting monsters, and they are very simple, they don't have a complicated mythology like vampires or aliens. They just keep coming at you, they're the never-ending presence of death. It gives a licence for violence, in a way.''

Mazzara is 45 and has been working in TV since he was 31. He came to it from eight years as a hospital administrator, running the logistics of an emergency room. ''It was great training for a TV show because I feel like every episode that comes in is like a patient. Some are healthy, some are sick and maybe they need a transplant or a new scene or reshoots or something.''

He knows what it's like to be on the operating table, too. His first writing job was on the Don Johnson cop show Nash Bridges, and he admits it wasn't his finest hour.

Do you remember the first line you wrote that went to air, I ask.

''Yes, yes I do,'' he says, confessing it came 15 minutes into his script, which meant ''the producers had clearly rewritten it''.

Mazzara's first line finally arrived as Nash stood over the body of a villain who had been shot dead, the only clue to his identity a tub of hand lotion from a neighbouring hotel. Nash looked at the hand cream and said: ''This guy is not only smooth, he's silky.''

''Isn't that terrible? Isn't that awful?'' Mazzara shrieks in shame. ''That's the first line I wrote. How horrible is that?''

Pretty horrible, Glen. But the good news is, things got better. Here's hoping they do again.

The Walking Dead returns to Foxtel's FX channel from Tuesday. The Writers Studio is at RMIT Storey Hall and The Wheeler Centre, Melbourne, February 23-25. Details: epiphany.com.au.